A joint tissue, such as knee joint or shoulder joint tissue in particular, is covered with a cartilage tissue at the top of bones which are linked by a joint so as to prevent direct friction therebetween. Damage of the cartilage tissue due to aging, enormous or repeated loads thereon will cause inflammation in a joint, resulting in arthralgia on a patient. In fact, damaged joint cartilage tissue and arthralgia are highly frequently found in both young and aged patients. In order to improve their quality of life (QOL) and even provide more effective treatment in view of medical economics, development of effective and efficient joint treatment method is increasingly required.
In the treatment of damaged cartilage tissue, the most major problem is to find out a method for regenerating such a cartilage tissue, which is difficult to naturally regenerate in vivo by drug administration, etc. For example, microfracture method that generates numerous microholes on a subchondral bone forms a fibrocartilage, but no hyaline cartilage as a normal articular cartilage is regenerated. Consequently, a damaged cartilage tissue is normally treated by transplanting an in vivo cartilage tissue.
Joint treatment methods by transplanting an in vivo cartilage tissue are generally classified into 2 types: autologous osteochondral transplantation method (Mosaicplasty) and cultured autologous chondrocytes transplantation (implantation) method. The autologous osteochondral transplantation method (Mosaicplasty) harvests an autologous cartilage tissue from a normal part of damaged joint or a joint tissue opposite thereto using a bone plug and transplants it to a defect portion. However, this treatment method involves one inevitable problem, i.e., damage of a normal cartilage adjacent to a defect cartilage harvested, and another problem of insufficient amount of a cartilage portion to be transplanted from a significantly damaged cartilage tissue in vivo. Meanwhile, the method harvests part of an autologous cartilage (hyaline cartilage) tissue in a patient and cultures it on an appropriate medium and/or a culture substrate to regenerate the cartilage tissue in a test tube and transplant it to an affected area. The cultured autologous chondrocytes transplantation method poses various problems: preparation of extremely expensive facilities required for aseptic culture of cartilage tissue, need for both harvesting and transplantation of cartilage tissue, higher treatment costs due to a long duration of patient's hospitalization, zoonotic risk due to contamination from culture process and unreliable treatment effects.
In order to avoid these problems, the development of a treatment method for promoting natural regeneration of cartilage tissue in vivo is of crucial importance. Current experimental methods include local administration of cytokines such as b-FGF and OP-1 to a joint containing damaged cartilage tissue in addition to a carrier, and administration of autogenous mesenchymal stem cell and ES cell to a joint containing damaged cartilage tissue. However, due to insufficiently known medical effects and problems like side effects, these methods are not served as practical application.